In the application of non-destructive inspection and human body inspection, two types of technologies are generally utilized: an imaging technology using radiation beam for transmission and an imaging technology using radiation beam for backscattering. Where backscatter imaging is employed, a subject to be inspected is scanned by radiation beam, i.e. a pencil beam, simultaneously the detector receives signal representative of radiation scattered back from the subject. A scatter image can be reconstructed or obtained based on the detected signals which are correlated with scanned positions or portions of the subject to be inspected.
Conventional flying-spot scanning mechanism implements a first dimension scanning by rotation motion of the rotary shield body with multiple collimation holes within a ray scanning sector while carrying out a second dimension scanning by swing or translating the ray scanning sector.
However, in the arrangement of the above-mentioned rotary shield body with multiple collimation holes, a relatively complex flying-spot formation mechanism is used and it has disadvantage on shielding of the X-ray and the leakage of the X-ray is hazardous to human body.
Further, when implementing the first dimension scanning, the scanning device carries out a non-uniform scanning on the subject in a vertical plane. More specifically, the scanning ray accelerates at the starting and ending of one single pencil beam scanning operation. As a result, the scanning spot will be further enlarged longitudinally at the starting and ending points of one single pencil beam scanning operation where geometric deformation of the scanning spot occurs. Accordingly, a longitudinal compression deformation due to variation of the scanning velocity of the scanning takes place in addition to the geometric deformation of the resultant image.
Furthermore, for the operation of the second dimension scanning, if a translational movement of the ray scanning sector is performed, the ray generator, the rotary shield body, and so on is required to translate in the second dimension, this renders the mechanical configuration of this device rather complicate; and if a rotation motion of the ray scanning sector is performed, rotational inertia of the ray generator and the rotary shield body should be overcome. This gives rise to a problem concerning wear and tear or breakdown of bearings of the rotating driver and the rotating ray generator and the rotary shield body.
In addition, in the prior art, the radiation source, for example the X-ray tube, is generally disposed inside the rotary radiation body, so it is difficult to match interface of the scanning mechanism with that of the conventional X-ray tube. Consequently, it necessitates redesigning the shield body of the X-ray tube so as to achieve matching the same with the interface of a conventional X-ray tube, which in turn increases the cost of the scanning device for backscatter imaging.